I've mostly got the process worked out. My sealer is a little too glossy, but other than that they look nice.

I picked up some "clear" mailing labels that are full sheets at staples. They're not clear. They kind of look like frosted glass. I printed to one, and stuck it on a foil to little effect. Then I sprayed it with sealer. The foil showed through. Looking into this method a bit more.